pH-tailored monodispersed nanopolystyrene: environmental impact on PGPR and nitrogen cycling in agricultural soils

Emulsion polymerization was optimized to synthesize polystyrene nanoparticles (NPSt) with tailored sizes by adjusting pH and azobisisobutyronitrile (AIBN) content. An NPSt sample prepared with 20 mg AIBN at pH 8 showed the smallest size (88 nm) and narrowest distribution (24 nm peak width). XRD patterns indicated semi-crystalline nature for this optimized sample. The involvement of synthesized NPSt in the nitrogen (N) cycle enhanced our understanding of nitrogen transformations and the response of microbial populations to polystyrene nanoparticles in the environment. In vitro experiments revealed compatibility of NPSt with tested PGPR strains, with no inhibition zones observed. Furthermore, carrot growth in soil containing 400 mg/kg NPSt showed no significant changes in biomass or shoot height compared to control soil. This demonstrates the NPSt samples had no negative effects on PGPR or soil nitrogen transformations and bacterial communities. Overall, the study optimized the synthesis of NPSt, evaluated environmental impacts on soil nitrogen cycling and PGPR, and found no toxicity of NPSt on PGPR or carrot growth up to 400 mg/kg concentration. The insights contribute to understanding nanomaterial interactions in agricultural systems, highlighting the need to consider the environmental impacts of nanoparticles.